The processing of a substrate of a semiconductor product or the like needs to be carried out in an environment in which high cleanliness is ensured. In general, the processing is carried out in a clean room that is entirely kept highly clean. However, heavy investment in facilities and immense expenses of maintenance are required in order to keep the entire room having a large cubic volume highly clean. Even after an investment in facilities has been made, further heavy investment in facilities would be needed in changing the layout of the room associated with a change in manufacturing process, which is not economical.
Further, substrates such as silicon wafers have been increasing in size, so such a measure is problematic in terms of the cost to ensure a required clean environment.
In view of the above, a method as disclosed in the specification of Japanese Patent No. 3167970 has been known in recent years, according to which the inside of a substrate processing device (hereinafter referred to as a clean device) for processing a substrate such as a semiconductor is kept highly clean as a micro environmental space (hereinafter referred to as a mini-environment portion), instead of keeping the entire room highly clean, thereby achieving the same effect as in the case where the entire room is kept highly clean.
That is, the substrate processing device is laid out in a room where substrates are manufactured, and a substrate storing container (hereinafter referred to as a clean box) whose inside is kept highly clean is used to transfer substrates into and from the clean device. Then, the clean box is coupled to a predetermined substrate gateway provided in the substrate processing device so as to prevent the entrance of dust from the outside. If substrates are transferred via the predetermined gateway, the entire environment to which those substrates are exposed can be kept highly clean without enhancing the cleanliness of the room where those substrates are manufactured. Thus, the same effect as in the case where the entire room is turned into a clean room can be achieved. As a result, an efficient production process can be realized by cutting down on the amount of investment in facilities and the expense of maintenance. In this specification, a substrate should be construed to include, for example, an exposure mask (reticle), a semiconductor wafer. Therefore, a substrate processing device should be construed to include a reticle processing device and a semiconductor wafer processing device.
A pod having an opening portion in a vertically lower side as described above and adapted to open and close the opening portion by vertically moving a lid is generically referred to as a standard mechanical interface (SMIF) type pod. The present invention relates to this SMIF type pod. As described above, an efficient production process is realized while reducing the amount of investment in facilities and the expense of maintenance and achieving the same effect as in the case where an entire plant is turned into a clean room, by adopting a so-called mini-environment method in which only limited space is kept highly clean.
A clean device 1 will be described with reference to FIG. 9. FIG. 9 is a view showing a cross-section of the entire clean device 1. The clean device 1 is provided with a processing room 60, a transfer room 50, and a load port portion 10.
Various substrate processings to be carried out in the clean device 1 are carried out in the processing room 60.
The transfer room 50 has therein a sealed-up space shut off from the outside. A robot arm 55 for transferring substrates is arranged in the transfer room 50.
A clean box 2 is laid on the load port portion 10 to transfer substrates into the processing room 60 of the clean device 1. The load port portion 10 has a function of removing a lid 2b from a main body 2a of the clean box 2.
A port door 3 that is substantially horizontally held is arranged in the load port portion 10. The port door 3 is raised and lowered vertically (see, Japanese Patent Application Laid-open No. 2001-203253). Referring to FIG. 9, the port door 3 is in its lowered state. The port door 3 is surrounded by wall surfaces surrounding the port door 3 on all four sides and a bottom portion located substantially parallel to a lower face of the port door 3. The wall surfaces and the bottom portion constitute a buffer chamber 6 inside the load port portion 10. The buffer chamber 6 is open at its top, thus constituting an access opening 5 that is substantially equal in size to the port door 3. Therefore, when viewed from the access opening 5, there is formed the buffer chamber 6 having a predetermined depth. The size of the access opening 5 is substantially equal to or smaller than that of an envelope region of an opening of the clean box 2. The port door 3 is raised and lowered along the wall surfaces of the buffer chamber 6. The access opening 5 is covered with the main body 2a of the clean box 2 as shown in FIG. 9 when the clean box 2 is laid on the load port portion 10. The buffer chamber 6 of the load port portion 10 remains sealed up even when the lid 2b is removed.
In this example, a pod 2 accommodates, instead of a substrate, a photomask called a reticle used in a semiconductor processing process. The inside of the pod 2 is filled with a gas such as dry nitrogen which is usually kept highly clean, when an article is accommodated therein. Using this gas, the pressure inside the pod 2 is thus held equal to or higher than an atmospheric pressure to thereby reduce the possible internal contamination resulting from an ambient environment.
The buffer chamber 6 in the load port portion 10 and an inside 50a of the transfer room 50 communicate with each other through a transfer opening 51. The inside 50a of the transfer room 50 and an inside 60a of the processing room 60 communicate with each other through a transfer opening 52. The inside of the load port portion 10, the inside 50a of the transfer room 50, and the inside of the processing room 60 are sealed up to be shut off from the external environment, thus forming a mini-environment portion.
Further, the transfer opening 51 is opened and closed by an opening/closing door 53 driven by an opening/closing gate valve 53a. On the other hand, the transfer opening 52 is opened and closed by an opening/closing door 54 driven by an opening/closing gate valve 54a. 
Referring now to FIG. 10, the load port portion 10 will be described in detail. FIG. 10 is a view showing the load port portion 10 of FIG. 9 on an especially enlarged scale. As shown in FIG. 10, the port door 3 is in its raised state unlike in the case of FIG. 9. Referring to FIG. 10, the lid 2b is laid on the port door 3. Note that, the port door 3 in its lowered state is indicated by a chain double-dashed line in FIG. 10. Raising/lowering means 4 is connected to the port door 3. The raising/lowering means 4 is provided with a latch opening/closing shaft 4a, a frame 4b for holding an actuator within the latch opening/closing shaft, a raising/lowering shaft 4c, and an electric actuator 7. The latch opening/closing shaft 4a is a vertically extending rod-like member that is joined at one end thereof to the lower face as an inner face of the port door 3, thus serving to directly transmit a raising/lowering movement of the raising/lowering means 4 to the port door 3. The latch opening/closing shaft 4a is joined at the other end thereof, which is located on the side opposite to the port door 3, to the frame 4b. The frame 4b is connected to the raising/lowering shaft 4c. The raising/lowering shaft 4c is connected to the electric actuator 7. Thus, the raising/lowering means 4 causes a raising/lowering movement of the port door 3. A through-hole through which the latch opening/closing shaft 4a extends is arranged at a lower center of the buffer chamber 6. The size of the through-hole is substantially equal to or smaller than that of the latch opening/closing shaft 4a. 
A rotary shaft 33 rotatable around a center of the latch opening/closing shaft 4a is mounted therein. Rod-like latch pins 32 arranged so as to protrude vertically from the surface of the port door 3 are arranged at a tip of the rotary shaft 33. The latch pins 32 are arranged at arbitrary positions on a circumference of a circle spreading around a rotation axis of the rotary shaft 33. It is preferable that the latch pins 32 be circular holes arranged point-symmetrically on the circumference of the circle.
The port door 3 is a rectangular flat plate substantially corresponding in shape to the access opening 5. When being raised, the port door 3 is fittingly inserted into the access opening 5 and closes it as shown in FIG. 10, thus sealing up the buffer chamber 6 and shutting it off from the external world. A positioning pin 3c as a protrusion, which protrudes from a top face of the port door 3 substantially perpendicularly thereto, is arranged on the top face side of the port door 3 corresponding to the outer face side of the load port portion 10 so as to position the lid 2b of the clean box 2. A hole corresponding to the positioning pin 3c extends through the lid 2b of the clean box 2. When the clean box 2 is laid on the load port portion 10 and the port door 3 is raised to abut on the lid 2b of the clean box 2, the positioning pin 3c is fittingly inserted into the hole so that the lid 2b is located at a right position with respect to the port door 3.
A lower portion of the port door 3 constitutes a flange-like brim 3a that is larger than the access opening 5. A sealing member 3b is fitted in the brim 3a. When the electric actuator 7 is driven to raise the latch opening/closing shaft 4a to thereby fittingly insert the port door 3 into the access opening 5, the brim 3a comes into abutment with an edge portion 5a of the access opening 5, thereby sealing up the buffer chamber 6. On the other hand, conversely, when the electric actuator 7 is driven to lower the latch opening/closing shaft 4a to thereby lower the port door 3, the access opening 5 opens widely.
A bellows 31 is so fitted as to range from a lower face of the port door 3 to at least an outer periphery of the latch opening/closing shaft 4a in the buffer chamber 6 (e.g., see Japanese Patent Application Laid-open No. 2001-203253 or Japanese Patent Application Laid-open No. 06-268046). When the electric actuator 7 is driven to raise the latch opening/closing shaft 4a, the bellows 31 expands because the port door 3 moves away from the bottom face. When the electric actuator 7 is driven to lower the latch opening/closing shaft 4a, the bellows 31 contracts because the port door 3 moves toward the bottom face.
A measure against falloff of the lid 2b from the main body 2a of the clean box 2 during transfer is taken by means of a latch mechanism. FIG. 11 shows a latch mechanism inside the lid 2b. 
A conventional latch mechanism typically has the following structure. A rotatably arranged circular rotary cam plate 21 is rotatably located substantially at a central position of the lid 2b. Latch holes 21a located at arbitrary positions on a circumference of a circle spreading around a center of the rotary cam plate 21 are formed therethrough. Note that the latch holes 21a are preferably circular holes arranged point-symmetrically on the circumference of the circle. The latch pins 32 engage the latch holes 21a. The latch holes 21a are shaped so as to receive the latch pins 32 therein, and are so arranged as to correspond in position to the latch pins 32.
Arranged outside the latch holes 21a of the rotary cam plate 21 are two cam grooves 23, which are point-symmetrical to each other with respect to the center of the rotary cam plate 21. Given that each of the cam grooves 23 has one end as a starting point 23a and the other end as an end point 23b, the distance between the starting point 23a of the cam groove 23 and the center of the rotary cam plate 21 is the shortest, whereas the distance between the center of the cam groove 23 on the end point 23b side of the cam groove 23 and the center of the rotary cam plate 21 is the longest. On the other hand, the lid 2b has a latch member 26 movable parallel to the plane of the lid 2b. A driven pin 24 is arranged on the rotary cam plate 21 side of the latch member 26. The driven pin 24 is engaged with the cam groove 23. The latch member 26 includes a tip portion protruding from a lateral face of the lid 2b. 
Now, when the latch pins 32 arranged at the tip of the rotary shaft 33 in the latch opening/closing shaft 4 of the port door 3 on which-the lid 2b is laid are fittingly inserted into the latch holes 21a and the rotary cam plate 21 is rotated by rotating the rotary shaft 33, the driven pin 24 of the latch pin 26 moves along the cam groove 23b from its starting point 23a toward its end point 23b. In accordance therewith, the position of the driven pin 24 moves from the center of the rotary cam plate 21 toward the outside thereof. In accordance with a moving distance of the driven pin 24, a tip portion 22a of the latch member 26 moves toward the outside of the lid 2b. The latch member 26 is set to be confined within the lid 2b when the driven pin 24 is located at the starting point 23a, and to protrude from the lid 2b when the driven pin 24 is located at the end point 23b. On the other hand, a latch hole 30 for engagement with the latch member 26a is arranged at the position where the latch hole 30 abuts on the lid 2b for the main body 2a of the clean box 2, so the lid 2b can be fixed to the clean box 2 by rotating the rotary cam plate 21.
The rotatable latch pins 32 for engaging the cam grooves 23 of the rotary cam plate 21 are arranged as an opening/closing mechanism on the top face of the port door 3. The latch pins 32 are coupled to the rotary shaft 33 arranged within the latch opening/closing shaft 4a. The rotary shaft 33 is coupled to a rotary actuator 34 as rotation means.
Next, how a substrate 9 is exchanged between the load portion 10, the transfer room 50, and the processing room 60 in the clean device 1 will be described.
The clean box 2 is first laid on the load port portion and fixed as shown in FIG. 9. At this moment, the substrate 9 is laid on the lid 2b. When the latch opening/closing shaft 4a is raised by driving the electric actuator 7, the port door 3 is raised while the bellows 31 expands, and the latch pins 32 protruding from the top face of the port door 3 are fittingly inserted into the latch holes 21a. Then, the port door 3 comes into abutment with the lid 2b of the clean box 2. When the rotary actuator 34 is rotated at this stage, the rotary shaft 33 rotates. In response thereto, the latch pins 32 press the edges of the latch holes 21a, thus causing the rotary cam plate 21 to rotate. When the rotary cam plate 21 rotates, the driven pin 24 rotates and the latch member 26 is confined within the door 2b. In this state, the lid 2b fixed to the main body 2a of the clean box 2 is then released therefrom.
When the electric actuator 7 is then driven to lower the latch opening/closing shaft 4a, the port door 3 is also lowered while the bellows 31 contracts. The lid 2b moves due to its own weight away from the main body 2a of the clean box 2 as the port door 3 is lowered. After the port door 3 has been completely lowered, the lid 2b on which the substrate 9 is laid is located on a bottom portion of the buffer chamber 6. In this state, the robot arm 55 can then perform a transfer operation.
The buffer chamber 6 in the load port portion 10 and the inside 50a of the transfer room 50 communicate with each other through the transfer opening 51, and the inside 50a of the transfer room 50 and the inside 60a of the processing room 60 communicate with each other through the transfer opening 52. The inside of the load port portion 10, the inside 50a of the transfer room 50, and the inside of the processing room 60 are sealed up and shut off from the external environment, thus forming a mini-environment portion.
When the opening/closing gate valve 53a is driven to open the opening/closing door 53, the buffer chamber 6 in the load port portion 10 and the inside 50a of the transfer room 50 communicate with each other. The substrate 9 is transferred from the buffer chamber 6 in the load port portion 10 by operating the robot arm 55. Furthermore, the inside 50a of the transfer room 50 and the inside 60a of the processing room 60 communicate with each other by driving the opening/closing gate valve 54a to open the opening/closing door 54. The substrate 9 is transferred from the transfer room 50 into the processing room 60 by operating the robot arm 55.
Note that included in related art documents about the above-described constructions are Japanese Patent No. 3084827 and Japanese Patent No. 2960540 as well as the aforementioned Japanese Patent Application Laid-open No. 2001-203253 and Japanese Patent Application Laid-open No. 06-268046.
In an SMIF type container, a latch member arranged on a lid or a tip portion of the latch member engages a hole or a groove formed in a main body of a pod, so that the lid is fixed to the main body of the pod. That is, this fixation is accomplished when the latch member comes into contact with a latch member receiving face formed on the main body, and a load toward a central portion of the lid and a load toward the main body are applied from the latch member receiving face to the latch member. In this case, as described in Japanese Patent No. 3167970 as well, a physical “rub” occurs between the surface of the latch member and the latch member receiving face so as to obtain the aforementioned loads, which may result in generation of particles. As far as a single operation is concerned, such particles are generated with very low frequency. However, in a working process consisting of several tens of steps or more, a considerable amount of particles may be generated.
In order to reduce the factors for generation of such particles, according to the aforementioned Japanese Patent No. 2960540, two cam faces acting in different directions are provided for a latch member. That is, a latch tip portion moves without coming into contact with a latch receiving face in advancing or retreating with respect to an inside of a main body portion such as a groove. The latch tip portion moves substantially perpendicularly to the latch receiving face in the process of engagement. Therefore, in the construction disclosed in the above document, the latch tip portion and the latch receiving face seldom rub each other. Accordingly, with this construction, it seems possible to suppress the generation of particles resulting from the rubbing of the latch tip portion which has been conventionally deemed problematic. However, the latch tip portion usually operates as a fulcrum for pressing the entire lid against the main body portion. Therefore, as is the case with the foregoing construction, loads tend to converge on a contact point when this contact point is obtained by a movement of the latch tip portion in the direction substantially perpendicular to the latch receiving portion. As a result of the convergence of the loads, there may occur a serious local abrasion. In this case, the generation of particles due to a cause slightly different from those of conventional cases seems to raise a problem.
Note that, the pressure inside a pod and the pressure inside a buffer chamber in a load port are generally held equal to or higher than an atmospheric pressure by means of a clean gas. Thus, even when the aforementioned particles and the like are generated, they hardly enter the inside of the pod or the like. Thus, even with the construction disclosed in Japanese Patent No. 2960540, it is possible to achieve an effect of reducing the amount of particles to some extent. However, in the case of an SIMF type container used for a specific purpose such as accommodation of a reticle, the inside of a pod is usually maintained in a depressurized state, and an operation of taking out the reticle as an accommodated article is also performed with the inside of a buffer chamber depressurized. In this case, generated particles are extremely likely to enter the inside of the pod or the like.
In consideration of the foregoing circumstances, there is known a construction in which a vacuum space is formed on a lid face on a main body side instead of employing a latch mechanism and the atmospheric pressure applied to the lid due to the existence of the vacuum space is used to ensure tight contact between the lid and the main body and seal up of an inner space. This construction eliminates the necessity of a latch mechanism, so it is absolutely unnecessary to consider the generation of particles resulting from the mechanism. In this construction, the lid is unlikely to fall off even when the pressure in the vacuum space has become equal to the atmospheric pressure for some reason, as long as the construction is applied to a container having an opening in its lateral face, such as a so-called FOUP. It is also relatively easy to cope with such a situation. However, a vacuum break in the space can cause the lid to fall off when the above-described construction is applied to a container having an opening in its vertically lower face, such as an SMIF type pod, so it is desirable to take an appropriate measure. In this case, when the above-mentioned latch mechanism is employed as a corresponding measure, the amount of the aforementioned particles needs to be reduced as well.